If terminals in adjacent areas use D2D to directly communicate, many benefits, such as a higher rate, a lower delay and a lower power consumption, can be brought to the terminals, at the same time, the wireless resource efficiency of operators are improved greatly, and the Relay mode of D2D is beneficial for the operators to improve the wireless coverage; for applications, using neighborhood information of a D2D communication process can develop more attractive new services. A Public Safety (PS) system can also use the D2D technology to achieve communication between the terminals when there is no wireless coverage.
FIG. 1 is a schematic diagram of a 3GPP-related D2D architecture according to the related art; as shown in FIG. 1, functions of key network elements are described below.
A terminal, which is also called User Equipment (UE), is supported that the terminals directly find each other via an air interface and directly communicate without a network.
A core network gateway, which is also called a Packet Data Network Gateway (PDN GW), is used for providing an access point for the terminal to access a PDN network, and mainly functions include assigning an IP address for the terminal, forwarding a data packet sent by the terminal to a corresponding PDN network via IP, mapping the data packets issued by the PDN network to different bearers according to different flows, and then sending the data packets to the terminal.
A home subscriber server is in a home network, and mainly functions are providing subscription information and authentication information of users and applications.
A near field communication server is outside the PDN GW, and mainly functions include D2D service authorization, and assigning a temporary code for the application requested by the terminal so as to used for terminal broadcasting, assist with D2D discovery and charge, etc. At present, only one near field communication server is deployed in one Public Land Mobile Network (PLMN).
There are three types of near field communication servers according to whether a user is in a roaming state. The first is a home near field communication server, which is in a home PLMN of a subscriber, and mainly functions are obtaining subscription information of user from the home subscriber server, and performing the D2D service authorization according to the subscription information. The second is a visited near field communication server, which is in a PLMN of a roaming location when the user is roaming, and mainly functions are checking whether the user in the roaming state is allowed to perform D2D services in the network according to a local policy, including sending a D2D signal and monitoring the D2D signal. The third is a local near field communication server, which is in another network, except for a visited network, at the location in which the user is located and covered with signals, and the network is also called a local network. There may be multiple local networks at the current location of the user, and mainly functions are checking whether the user is allowed to monitor the D2D service in the network according to a local policy.
FIG. 2 is a schematic diagram of a D2D service authorization process. The flow includes the following steps.
In step S201: after establishing a connection with the PDN GW and obtaining a user IP address from the PDN GW, a terminal sends an authorization request to a home near field communication server. The terminal inquires a corresponding IP address through a Domain Name Server (DNS) according to a Fully Qualified Domain Name (FQDN) of the home near field communication server, and then communicates with the address. The FQDN of the home near field communication server can be either statically configured in the terminal or deduced according to a home PLMN ID. The IP address of the home near field communication server can also be configured in the terminal. The authorization message contains information about the PLMN which the user is currently in and a user identity, for example the International Mobile Subscriber Identity (IMSI) or the Mobile Subscriber International ISDN/PSTN Number (MSISDN), herein the ISDN is short for Integrated Service Digital Network, and the PTSN is short for Public Switched Telephone Network.
In step S202: if there is no subscription information of user in the home near field communication server, the home near field communication server requests the home subscriber server for the subscription information of user, and the request carries the user identity; the home near field communication server stores the subscription information in the local database after obtaining it.
In step S203: the home near field communication server returns D2D authorization information of the user according to the subscription information of user and local configuration, the authorization information includes: a PLMN list permitting full authorization of the D2D service, a PLMN list permitting condition authorization of the D2D service, and a local PLMN list of the current location of the user.
In step S204: for the PLMN list permitting full authorization of the D2D service, the UE can directly initiate the D2D service in the PLMN; for the LMN list permitting condition authorization of the D2D service, the user needs to authorize in the PLMN again; the user selects the PLMNs that are overlapped in the PLMN list permitting condition authorization of the D2D service and the local PLMN list provided by the home near field communication server, and then initiates authorization to the PLMN. The PLMN may be either a local network or a visited network. The terminal deduces FQDN information of the near field communication server from information about the selected PLMN, inquires the DNS to obtain the IP address of the near field communication server of the PLMN, and then initiates an authorization request to the address, the request carries the user identity.
In step S205: the local/visited near field communication server obtains FQDN information of the home subscriber near field communication server according to the IMSI of the user, inquires the DNS to obtain the IP address of the home near field communication server, and then initiates an authorization request to the address, the request carries the user identity.
In step S206: the home near field communication server returns an authorization response.
In step S207: the local/visited near field communication server returns the authorization result back to the terminal according to the local configuration to indicate whether the terminal is allowed to conduct the D2D service in the network.
If the terminal needs to authorize multiple local/visited near field communication servers in step 204, the steps from step S204 to step S207 are repeated.
After that, the terminal decides whether to initiate the D2D service according to the authorization result.
There are two problems in the above process; the first problem is that in step S203, the home near field communication server needs to configure all the local PLMN lists at the location of the user, when the lists change, all the near field communication servers in the network need to update, so it is very difficult to operate; the second problem is that in step S204, the terminal may be unable to communicate with the local/visited near field communication server, unless the current PDN GW and the local/visited near field communication server are in the same network, or the local/visited near field communication server has an externally reachable IP address, but in many cases, the above conditions cannot be satisfied, so the D2D service authorization will not be realized.